Yeah, that part could be purely operational. Universal has you go through the line and do an immediate swap inside. Disney used to do some swaps that way back in the day before FP+.
I think the only real question is if the group is going SB and that line is longer than one hour how will they handle the time on your pass. It could be it will be set up like
DAS where they will take the SB time and factor it in to the ride time. The computers would automatically determine that and could be there will be more than an hour leeway. Maybe the system will automatically at the SB time to the hour.
No reason it can't work, it's up to guests to manage their time and party well while waiting. We all decide when we travel, what our party makeup is and it's our job to make the most of our trips. We always took waiting group to bathroom, get drink/snack, find some A/C, go on a shorter line ride .... then be back to the ride ready to swap when they got off.
We have to remember this service was offered BEFORE FP+ ever existed. Disney never kept up the processes with the existing operation and maybe now they have decided to make it more functional for operations, and eliminate some of the loops and abuses.